Technology & Coding

How the Internet Actually Works

Understand what really happens between typing a web address and seeing the page, from packets to DNS to encryption.

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What you will learn about How the Internet Actually Works

The 7-day sprint
  1. Packets and Packet Switching. The internet moves data by chopping it into small, independently addressed chunks called packets that travel separately and get reassembled at the far end.
  2. IP Addresses and Routing. Every device on the internet has an IP address, and routers forward packets toward that address one hop at a time without any single machine knowing the whole path.
  3. DNS, the Internet's Address Book. DNS translates human-friendly names like wikipedia.org into IP addresses using a distributed hierarchy of servers, and almost nothing online works without it.
  4. TCP, UDP, and Ports. Above raw packet delivery, TCP adds ordering, retransmission, and congestion control, UDP stays fast and unreliable, and port numbers decide which program on a machine receives the data.
  5. HTTP and HTTPS. The web is one application built on top of the internet: browsers send HTTP requests, servers return responses, and TLS wraps the whole exchange in encryption.
  6. The Physical Internet and Who Owns It. The internet is not a cloud but glass, copper, radio, and buildings, owned by thousands of independent networks that voluntarily interconnect and exchange routes with each other.
  7. The Full Journey of a Page Load. Everything from the week combines in a single ordered sequence, and knowing that sequence lets you reason about why any specific connection is slow or broken.
The 80/20: the 7 concepts that matter most
  • Packet switching and best-effort delivery
  • IP addressing and hop-by-hop routing
  • DNS name resolution
  • The layered stack and the end-to-end principle
  • TCP versus UDP, plus ports
  • TLS, certificates, and what encryption does not hide
  • Latency, bandwidth, and caching or CDNs
The core idea, explained like you are 5

The internet is a way of sending messages by cutting them into small addressed pieces and passing them hop by hop between independently owned networks that all agree on the same addressing rules.

Then the quiz and the ladder

10 questions that correct you when you are wrong, and beginner, intermediate, advanced levels, each with a practical exercise.